Hand control for electric motors



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Oct. 13, 1931. A. M. RIDDELL 1,327,372

v HAND CONTROL FOR ELECTRIC MOTORS Filed May 31. 1928 '@i'iII1HHHIIHHIMHHHHH ,4 fraz/Vey Patented Oct. 13, 1931 UNITED ASTATES ARTHUR I. BIDDELL, F LOS ANGELES, CAIUORNIA HAND CONTROL FOB ELECTRIC MOTORS l Application Med Iay 81, 1928. Serial No. 881,707.

. This invention relatesto a scheme for controlling electric motors, and especially to such motors that are arran ed to be supported by the hand and to pe orm such functions as beating, brushing, or scrubbing. x

It is'now quite common to provide a small electric motor to drive an egg beater or similar tools, such as a paint mixer, buffer, saw, grinder, or the like. Ordinarily, such motors are provided with .a grip or handle, and a trigger switch for energizing and deenergizin it.

uch motors obviousl cannot be regulated in speed by such `switc es, and it has been 1.; proposed to incorporate a controlling device, such as a rheostat in the structure. Such rheostats however must be controlled separately from the handle, and therefore two hands are needed for holding the motor and controlling it.

It is accordingly an object of my invention so to arrange a motor controller that the same hand that holds the motor can at the same time be used to control its speed.

Although various forms of controlling de- `vices can be used, I prefer to utilize a carbon pile rheostat, varying its resistance by a variation in the pressure exerted on the pile. I nd that I can conveniently incorporate such 3o a carbon pile device in the handle structure,

and that it can readily be controlled by one of the fingers of the hand grasping the handle, so as to vary the speed of the motor, or to stop the motor. It is accordin ly another object of, my invention to provi e a carbon pile type of control in con]unction with the supporting handle.

It is possible so to arrange the device that the motor speed can be maintained at a number of points even after the pressure of the finger is removed; and therefore it is still another object of my invention to make it possible alternatively to control the speed continuousl by a continuous pressure variation of the nger, or to control it step-by-step by the aid of a catch device that acts to hold the pile under pressure at any one of a number of stages of compression.

l My invention possesses many other advantages, and has other objects which may be made more easily apparent from a consideration of one embodiment of my invention. For this purpose I have shown a form in the drawings accompanying and forming part of the present specification. I shall now roceed to describe this form in detail, w ich illustrates the general principles of my invention; but it is to be understood that this detailed description is not to be taken in ay limitin sense, since the/scope-of m inven- ,o tion is est defined by the appende claims.

Referring to the drawings: Figure 1 is a side elevation of a moto equipped with a tool, and a speed controlling device that embodies m invention; Fig. 2 is an enlarge section through the handle of the motor; and

Fig. 3 is a detail section taken along plane 3-3 of Fig. 2.

In the present instance I show a small 1o electric motor 11 of the universal type, capable of operation either onl direct or alternating current. It is shown as provided with an extending shaft coupling 12, to which can be detachably coupled any of a number of tools; a beater 13 is shown.

In order to make the motor 11 readily l portable so that the tool driven thereby can utilized-wherever desired, a handle structure 14 is provided, fastened to the motor and so capable of being grasped by the hand of the user. Thus the tool such as 13 can for example be inserted in a receptacle for mixing paint or beating eggs, while the motor is supported by handle structure 14.

Alternativel the motor 11 can be detachably supporte on a pedestal 15. This pedestal has a circular portion 16 that extends into a socket provided in a member 17 fastened to the bottom of motor 11. A thumb screw 18 extending into the socket can be used to fasten the motor in any desired angular position with respect to pedestal 15. This pedestal can of course be fastened either to a horizontal or to a vertical surface, to position -the axis of shaft coupling 12 either horizonor verticall as desired. he motor 11 1s shown as fed with current through leads 19 extending through the bottom of handle 14. The speed control of the 100 tall motor is effected b one of the fingers of the hand that grasps tlie handle 14, which finger (preferably the thumb) acts on a control member 20, movable about an axis of pivot 21. This member has a shoulder 22 servirg as a convenient abutment for the thumb. t is apparent that the control of the motor 11 is very conveniently provided; but one hand is needed for supporting as well as for controlling the motor. The manner in which the speed controlling function is secured will now be described.

The handle structure 14 is hollow. The handle proper is made up of two halves 23 and 24 fastened together as by screws 25. These halves 23, 24, each has a half socket portion 26, 27 in which a tube 28 of insulation 1s clamped. A collar 29 formed integrally with socket 26-27 enters a corres onding groove in the tube 28. The other end) of tube 28 is fastened into a socket member 30 that is fastened to the top of motor 11'.

The hollow tube 28 serves as a convenient receptacle for the variable impedance used to control the speed of the motor 11. At the same time, it also serves as o ne of the supports for the handle. Preferably the variable impedance is formed byza series of carbon discs 31 forming a com ressible carbon pile rheostat. One end of t is pile rests on a metal terminal member 32 fastened in an insulation bushing 33 that is in turn fastened as by a dowel pin, to the socket member 30 and tube 28. A screw 34 engaging the rear side of terminal`32, can be used to fasten wire 35 in member 32. This wire leads to the motor, and extends through appropriate a ertures in the bushing 33 and 1n tube 28. he bushing 33 can form a plug in tube 28, and can be covered over by the end wall 36 of socket 30. The inside diameter of tube 28 is only slightly larger than the diameter of discs 31.

It is well understood that a carbon pile, such as formed b discs 31, has low resistance when placed un er pressure, and this resistance increases to a maximum as the pressure is gradually reduced to zero. I shall now describe how this pressure can be varied by operation of the control member 20.

A rod 37 of metal, having a head 38 is ar ranged axially of the pile 31, the head 38 engaging the end carbon disc. Axial movement of this rod is permitted in a guide 39 held in place as by a press fit in a bushing 40 held in the end of tube 38. Normally, rod 37 is urged away from pile 31 in order to release pressure thereon, as by a compression spring 41 placed between guide 39 and washer 42 fastened to guide 37. The control member 20, when moved in a clockwise direction around pivot 21, serves to-compress the spring 41, by acting on the rounded end of rod 37, and urges this rod to the right to impose a pressure onthe pile. pose, member 20 is provided with a portion 43 having a surface engaging the end of rod 37. This portion 43 1s inside the handle structure, and is connected with the external portion by a neck 44, extending through a slot 45 formed between handlehalves 23, 24.

The circuit for motor 1l extends through one lead 19, to guide 39, thence by way of spring 40 and rod 37 to pile 31, thence through terminal 32 and Wire 35 to the motor 11. The other lead 19 passes through a hollow tube 46 of insulation into member 17, thence to the motor 11. It is apparent that the pile 31 is directly inI series with the motor, and the speed can be increased by digital movement of control member 20 in a clockwise direction. When this member is released, the pressure on discs 31 is is practically an open circuit. The heat generated by the passage of current through the For this pur- .pile is dissipated through tube 28. This tube serves effectively to insulate handle 23-24 from the heat generated in motor 11; and the same function is served by the insulation tube 46. This latter tube can be fastened into handle 23, 24 and into member 17 in a man? ner similar to the fastening of tube 28.

It is seen that a continuous variation is provided by movement of control member 20. By releasing this member 20, the motor 11 can be deenergized. In some instances, the speed of the motor is to be maintained substantial! constant over a lon period; and under suc circumstances, the l'nger holding the member 20 would become fatigued. To obviate this,

. I provide an arrangement whereby the member 20 can -be latched in any one of a number of positions.

Thus for example, the bottom of portion 43 can be provided with a number of notches or serrations 47. Coacting with these is a spring pawl 48 that can be urged into a notch by urging a button 49 inwardly, ing fastened to spring 48 and extending out of handle 23, 24. The lower end of spring 48 is anchored in a stationary ost 50.

The mode of operation o awl 48 and part 43 can now be described. Wihen button 49 is not urged inwardly, the free end of sprin pawl 48 will be out of engagement wit notches 47. Member 20 can then be operated to produce the desired motor speed. When that speed is attained, button 49 is pressed, and urged in until stopped by the engagement of pawl 48 with one of the notches 47 The thumb can then be released from member said button beso slight that there i 20, which will be retained in its ldesired posi- 48, and button 49 snaps back into normal position. Then upon release of member 20, it will be urged by spring 41 to its extreme position, determined by the length of slot 45.

I claim:

1. In apparatus of the character described,A

a motor, a handle for the motor including a hollow tubular portion, a carbon pile in said portion for varying the s d of the motor, and means for varying t e pressure on the pile, said means being arranged to be controlled by the same hand that grasps the handle.

2. In apparatus of the character described, a motor, a handle structure for the motor, said structure includin' a hollow heat insulating tube interposed tween parts of the handle structure to prevent heat from the motor lfrom reachin the handle pro r, and means capable of a ecting the spee of the motor accommodated in said hollow tube, and means cooperating with. said first named means to vary the ressure thereon.

3. The combination as set forth in claim 2, in which the speed affecting means is a carbon pile rheostat.

4. In apparatus of the character described, a motor, a handle structure for the motor, said structure comprising a handle proper and a hollow portion extending therefrom, a variable im edance for varying the speed of the motor, ocated in said hollow portion, and a controlling member cooperating with said impedance and extending out of the handle, said member being capable 0f digital control for varying said impedance.

5. In apparatus of the character described, a motor, a handle structure for the motor, said structure having a hollow portion extending from the handle proper, a compressible carbon pile in said portion, for .va ing the speed of the motor, a rod movable axially of the ile to compress the pile, and a digital controFmember extending out of the handle for actuating said rod.

In testimony whereof I have hereunto set m hand.

y ARTHUR M. RIDDELL. 

